1. Field of the Invention
The present invention generally relates to a digital image processing device and an operating method thereof, and more particularly, to a method and apparatus for blurring an image background, whereby a moving image and focal distance information matched to the moving image according to a movement distance of an AF motor are obtained for the same object and background blurring is applied to a still image differentially, based on focal distances of the moving image and the still image.
2. Description of the Related Art
At present, commonly used digital image processing devices such as digital cameras, camera phones, smart phones, and the like include various digital elements for processing digitized data, thereby providing functions distinguished from those of analog photographing equipment.
For example, the digital image processing devices can store a large amount of image data, which far exceeds the amount of image data that can be stored in a conventional film, by using a large-capacity memory included therein, in which a charge coupled device (CCD) and the memory substitutes for a film in order to form a high-pixel image, thereby sharing image data with a personal computer (PC) and providing convenience in image processing.
Moreover, the digital image processing devices provide a higher number of functions, such as auto adjustment of shutter speed and aperture, auto focus, image enhancement, auto adjustment of light intensity, and the like, compared to those provided by analog photographing equipment.
However, since analog photographing equipment is manually operated, it may be preferred over the digital image processing devices when an expert delicately works with the analog photographing equipment.
In this regard, recently released digital image processing devices also implement unique functions of conventional analog image processing devices as well as beneficial functions of digital devices. In other words, the digital image processing devices integrate unique strong points of analog devices to overcome the challenges of digital devices and thus can provide various and specialized functions.
Moreover, with the wide spread use of digital image processing devices, the number of people who are interested in photography is gradually increasing and thus, the number of users who acquire professional photographing skills is also increasing.
However, the digital image processing devices are still deficient to meet professional users' demands in many aspects.
For example, in most cases with figure photographing, an out-of-focus effect is generally used. When a conventional digital image processing device is used, the implementation of the out-of-focus effect is almost impossible due to a lens and a CCD having limited sizes.
In general, the out-of-focus effect differs with the size of a “circle of confusion” and the size of the circle of confusion is closely associated with depth such as a depth of focus and a depth of field. When a dot of an object image is focused through a lens, it is focused in the form of a circular dot having a predetermined diameter from the minimum size that can be recognized as a dot. As the diameter of the dot increases, human eyes recognize the dot as being blurred. The circular dot which has the diameter that causes the dot to appear blurred is referred to as the circle of confusion. Thus, the depth depends on factors associated with the circle of confusion, such as the CCD size, the aperture, and the lens focal distance of a digital image processing device, a camera-to-object distance, and an object-to-background distance.
Among those factors that determine the depth, an image sensor, the aperture, and the lens focal distance, except for the camera-to-object distance, change by a large amount according to physical specifications of the digital image processing device. Due to the nature of a miniaturized digital image processing device, the digital image processing device can express only a deep depth at all times due to a small-size image sensor and a small-diameter lens, resulting in a failure to meet a user's need for a shallow depth (of field) in which a main object is clear while a background is blurred.
Moreover, when a large-sized image sensor and a large-diameter lens are adopted for optical features, such adoption may be associated with the yield of semiconductor processing for manufacturing the large-sized image sensor and may increase the cost and size of the digital image processing device because of a need to design the large-diameter lens, thereby hindering miniaturization of the digital image processing device.